Histidine residue content of photosystem ¢ò reaction center D1/D2/cytochrome b559 complex decreased by about 26% after illumination. The result suggests that some histidine residues are damaged by illumination. The damage of histidine residues may be related to the changes of the spectra properties during the incubation in the dark following preillumination of the reaction center complex.

In our previous papers, it was reported that peimine, peiminine, eduardine and three new alkaloids, zhebeinine, zhebeirine, zhebeinone, were isolated from the bulbs of Fritillaria thunbergii Miq. In consecutive investigation of the plant, an additional new alkaloidal glucoside, 5¦Á , 14¦Á -cevanine-6¦Á , 20¦Â-dihydroxyl-3¦Â-O-¦Â-D-glucoside, named zhebeininoside (¢ñ) and aknown picropodophyllotoxin (¢ò) were isolated. The structure of zhebeininoside was determined on the basis of spectral analysis and chemical reaction. Picropodophyllotoxin was firstly isolated from Fritillaria plants.

The organic free radicals in anthers were measured by electron spin resonance (ESR) spectroscopy during microspore abortion of male-sterile rice. The test lines were cytoplasmic male-sterile rice(CMSR) V20A, Zhen-shan 97A and Hubei photoperiod sensitive genic malesterile rice(HPGMR) W6154 and Nong-keng 58s. Anthers with different stages of microsporegenesis were vacuum desicated over phosphorus pentoxide then ground in a porcelain mortar. The organic free radicals in the powdered anthers were determined using a JES-Feixg ESR spectrometer and the signal amplitude andg factor were calculated. In all anthers examined, the organic free redical signal showed non-superfine structure with a g factor of 2.0024¨C2.0031. The levels of organic free radicals were related to the stages of microsporegenesis in both CMSR and HPGMR anthers. At trikaryophase of CMSR V20A and Zhenshan 97A, the signal was approximately 3.2 and 3.8 times stronger than that at dikaryophase, respectively. However, in the maintainance lines of these two CMSR, the changer was only 15¨C43% from dikaryophase to trikaryophase. The level of organic free radicals in HPGMR anthers, with dikaryophase microspore collected at different fertility transformation under field condition showed a gradual increase. Similar trends of increase were found with the abortion of microspore in anthers of HPGMR W6154s and Nongkeng 58s. Chlorophyll and carotinoid contents in anthers increased with different stages till dikaryophase, then markedly decreased at trikaryophase, which implays that the high ESR signal in abortive stage of microspore was not related to pigments. It is suggested that microspore abortion of male-sterile rice in both CMSR and HPGMR was associated with anomalous free radical metabolism, and its biochemical implication may be somewhat consistent with the aging and senescence process of etber organs.

Preliminary Studies on the Geographic Distribution of Fagus in ChinaAuthor: Hong Bi-gong and An Shu-qing
Journal of Integrative Plant Biology 1993 35(3)

There are 11 species in Fagus, 5 of them are endemic to China. They are the major trees of deciduous broadleaved forest in Northern temperate region. This paper mainly deals with the relationship between the distribution of 5 species and 5 climatic indices. The results showed that the principal factor controlling the distribution of Fagus was the precipitation in growing season. The climatic change which resulted from Himalayan movement and the changes during pogt-glacial period and human disturbance also affect the contraction of the range of distribution.

Anatomical differences between normal wo od and compression wood of masson pine (Pinus massoniana) were studied by means of light and scanning electron microscope. The results show that the normal wood is narrower han the compression wood in growth ring width. The transition from earlywood to latewood is abrupt in normal wood in contrast to the gradual transition in compression wood. In transverse section, normal wood tracheids appear more or less square and rectangular, whereas compression wood tracheids are round in shape with the exception of those at the vicinity of growth ring boundary. In consequence, intercellular spaces are prominent at the junction of tracheids in compression wood. Furthermore, the secondary walls of compression wood tracheids consist of only two layers, S1 and S2, in comparison with the three layers in normal wood. Helical cavities or checks present only in compression wood, spiraling around the tracheid in the same direction as the cellulose microfibrils. Finally, the factors responsible for the formation of compression wood are discussed as well.

This paper reports the studies on two species of fossil woods, which have been excavated from the northern part of Yanglou Town, Xinzhou County, the city of Wuhan, Hubei Province. According to the observation of wood anatomical features they were identified as Catalpa wuhanensis sp. nov. Yang and Gmelina wuhanensis sp. nov. Yang growing in Late Tertiary Period, which further proved the hot and humid climate during that period. Moreover, the fossil woods of the Lauraceae and the Legu minosae published earlier in Acta Bot. Sin. (1987) were further identified as Laurinoxylon wuhanense sp. nov. Yang and Acrocarpus fraxinifolius Arn. ex Wight.

Calli were induced from anther protoplasts in suspension cultures, and from mature embryo derived callus. After transferring the calli into plant differentiation medium, plantles were obtained. The protoplast plating efficiency and plantlet regeneration frequency were influenced not only by rice (Oryza sativa L.) genotypes but also by the age of suspension lines. The F2 anther-derived calli gave a protoplast plating efficiency of 4.5 %¨C9.6 % and plantlet regeneration frequency of 20.0 %--36.7 % using agarose-imbedded method. In comparative study of the agarose-imbedded culture and nurse culture, the latter method seemed to be more advantageous in time saving and high efficiency.

The development and structure of the floral nectaries of Capsella bursa-pastoris (L.) Medic. were examined. The nectaries consisted of four separated parts which were semiorbicular and were morphologically and anatomically similar to one another. They were located at the receptacle between stamens, and each part was composed of secretory epidermis, nectariferous tissue and vascular bundles, belonging to structural nectary. When the various floral organs were developed, 2--3 superficial layer cells of the receptacle between stamens became meristemoid and contributed to primordia the formation of nectary. By intercalary meristematic activity, the four nectaries formed synchronously. During the different stages of nectary differentiation, the content of starch gra ins and vacuolation in the cells of epidermis and nectariferous tissue changed regularly. According to the structural and histochemical changes the pre-nectar might be supplied by phloem. The nectar formed in nectariferous tissue was then secreted to the sub-stomatal chamber and where it was finally excreted from the stoma.

By treating the MoFe protein of nitrogenase from Azotobacter vinelandii with O-phenan-throline under anaerobic or aerobic condition, inactive MoFe protein which was partially deficient in P-cluster or in both P-cluster and FeMoco could be obtained. The above mentioned inactive MoFe proteins were incubated with a reconstituent solution containing Ma2MoO4, Na2S, dittnothreitol (DTT) and homocitrate or citrate. Results showed that the acetylene and proton reduction activity of nitrogenase could be restored in both treated proteins after incubating with the reconstituent solution containing either citrate or homocitrate, and their metal content, CD and MCD spectra which reflected the content of metal clusters in the MoFe protein could also be restored. But their restoration of the Ns-reduction ability of the treated MoFe proteins was significantly different from each other, the P-cluster deficient MoFe protein could be restored by a reconstituent solution containing either citrate or homocitrate, and the P-cluster pius FeMoco deficient MoFe protein could only be restored bythe reconstituent solution containing homocitrate. The result indicated that the P-cluster assembled by the reconstituent solution containing either citrate or homocitrate was similar to that of the native MoFe protein, and the FeMoco which was assembled only by the reconstituent solution containing homocitrate was similar to that of the native MoFe protein. These results further demonstrated that homocitrate is an essential component of FeMoco.

Comparative study on the subcultured callus of tobacco (Nicotiana tabacum L. cv. Willow leaf) has revealed that protein contents and pr otease activities slowly decreased in the callus during differentiation and bud formation. The synthetic rates of fraction ¢ò protein (water soluble protein and enzymes) and ribosomal hist one, the levels of total ribosomes, especially the levels of polyribosomes which function the protein synthesis, were higher in the differentiating callus than those in the subcultured callus. This indicates that protein synthesis in differentiating callus is greater than that in non-differentiating callus, and that the protein pattern synthesized in differentiating callus may differ from that in non-differentiating callus. During the late period of culture, the protease activities in subcultured callus rapidly increased, and the levels of polyribosomes, protein synthetic rates and protein contents apparently declined, which may be the result of metabolic changes in callus senescence. Meanwhile in the differentiating callus the protein contents, protein synthesis rates and polyribosome levels although somewhat declined accempanying the growth of formed bud, were still much higher than those in the subcultured callus.

A protease was crystallized from the fresh leaves of Agave sisalana by means of ethanol fractionation and chromatography on DEAE-cellulose. The enzyme crystals seen under microscope were shaped as regular hexogonal plants. The enzyme could be activated by cysteine and EDTA, and was reversibly inhibited by p-chlor omercuribenzoate, Hg2+, Ag+, Cu2+ and 5,5'-dithiobis (2-nitrobenzoic acid), irreversibly inhibited by iodoacetic acid at pH 7.5. These resuits showed that sulphydryl group was essential to the enzyme activity. The optimal pH of the enzyme for casein was about 7 5, and the optimal temperature was about 50¡æ. The Km value for casein was 0.0625 %. It was relatively stable at temperature below 45¡æ and at the. pH ranging from 6.0 to 10.0.

The screening of rice (Oryza sativa L.) variants resistant to blast was studied by using ¦Á-picolinic acid treatment. In order to establish the selection conditions, anthers and anther-derived calla of rice strain C2, which is susceptible to blast, were cultured ma media supplemented with different concentrations of ¦Á-picolinic acid to examine the response to ¦Á-picolinic acid. it was shown that callus induction frequency of anther and callus growth were obviously declined in relevance to the increasing the concentrations of ¦Á-picolinic acid. 40 mg/L of ¦Á-picolinic acid was the crucial concentration for anther-derived callus induction and growth of the rice strain C2. The callus lines tolerated to 40 mg/L of ¦Á-picolinic acid were selected from rice strain C2 and then regenerated into green plants. By identification of blastresistance in the seedling and boot stage of R1 and R2 generations, two variants No. 4-091 and No. 2-07 resistant to Pyricularia oryzae strain ZA1 and ZB11 were obtained, however, the grain yield per plant of these variants were not so high as C2.